This invention relates generally to a novel drafting table tray for use on a drafting board having a cable guide track mounting for its straight-edge assembly, which assembly is slideably adjustable on the cable guide track as is well known in the art. The tray is pivotally attached and pivotally adjustably positionable at each end thereof to a pair of base mounts which are slideably adjustable on the cable guide track. In addition, the base mounts have a friction pad on the bottom thereof to hold the tray in a desired location on the drafting board when the board is tilted, and a roller for easy movement of the mounts longitudinally from top to bottom of the board when the mount is tilted sufficiently to remove the contact between the drafting board and the friction plate.
In the past it has been common to provide trays for drafting boards which are pivotally adjustable to maintain the tray in a horizontal position to compensate for the drafting board being tilted. The patent to Ivester, U.S. Pat. No. 2,846,808 shows a drafting board tray which is tiltably adjustable to accommodate any angle of the drafting board and adjustably positionable along the surface of the table. However, in order to adjustably position the tray on the surface of the table, it is necessary to release four wing nuts and slide the bracket mounting of the tray in an elongated longitudinal slot, thus making it very inconvenient to change the position of the tray in order to work on portions of the drafting board being blocked by the tray. In addition, the brackets and tracks necessary for the apparatus shown in the patent to Ivester, which tracks must be underneath the drafting board and which brackets must then extend outwardly from the board sides, in order to allow the straight edge assembly to pass under the tray, can interfere with the lowering of some drafting boards on a drafting table to the fully untilted position.
It is well known in the art to use a continuous cable and a series of rotatable cable guides to position a straight edge assembly longitudinally up and down the surface of the drafting board. This is shown, e.g., in the patents to DeLisle and Koch, respectively, U.S. Pat. Nos. 2,194,889 and 1,568,850.
Rollers have been used to position adjustable trays on the surface of a drafting board. The patent to Miller, Jr., U.S. Pat. No. 3,643,605 shows a pivotally adjustable tray which is pivotally mounted on a strut. The strut extends longitudinally from top to bottom of the board and is positionable laterally across the board by rolling it on rollers contained in carriages attached to the upper and lower ends of the strut. However, the strut shown in the patent to Miller, Jr. depends on roller engagement of a lower guideway, projecting up from the lower end of the drafting board, for preventing the strut from sliding off of the table top when the board is tilted upward. Such a projection at the lower end of the drafting board is often undesirable. In addition, the longitudinal orientation of the strut necessarily limits the lateral extension, and thus the size, of the tray, without using an inconvenient plurality of struts, lest the tray become unstable when objects are set upon its lateral extremities. Further, at some angle of upward tilt of the drafting board, the tray will have the extension of its center of gravity outside of the surface of the drafting board and guideway, causing the top end of the strut to swing outwardly, absent some undisclosed track or guide to hold the strut top against the drafting board. The tray will thus fall off of the drafting board.
Thus it can be seen that the arrangements which exist in the prior art have, at best, a degree of utility in providing an adjustably positionable and pivotable tray for a drafting board. However, room for significant improvement remains.
The problems enumerated in the foregoing are not intended to be exhaustive, but rather are among many which tend to impair the effectiveness of previously known drafting board trays. Other noteworthy problems may also exist; however, those presented above should be sufficient to demonstrate that drafting board trays appearing in the art have not been altogether satisfactory.